Keep in mind that posting photos on your web site does not draw focus to your site to help sell the photos. You will need to drive attention to your site in order to sell, a marketing effort is needed.
Previously we created an SEO guide that may be helpful for you.
SmugMug Seo guide: https://cdn.smugmug.com/img/marketing/seo/guide.pdf
Thank you Chasing Daylight for linking to the guide: Though you posted it in 2022, how current is the guide? I am seeing terms (e.g. H1, H2, etc) in it that I do not see as I’m creating galleries and titling my images, etc. Also, SmugMug seems to encourage keywords and captions but the guide indicates that keywords are not so critical anymore. Perhaps I’m missing something in my understanding! Thanks!
Aside from making sure that your site uses the SEO guidance shared, I've found promoting the galleries of the sports games that I've covered via social media (Facebook, Twitter, Instagram) handy for signposting users to my site and generating sales from there.
Obviously it depends if you are looking to promoting single images or galleries of events/collections?
Personally I'd always recommend captioning and keywording (within reason) all of your images on your SmugMug site. This will help you manage your images, help users who are browsing your site and of course your SEO as well.